Method for manufacturing SiC ingots and SiC substrates, and method for evaluating SiC ingots.

Abstract

To provide an SiC ingot easy to be laser-processed.SOLUTION: This SiC ingot is made of an SiC single crystal inclined by an offset angle from a (0001) face and crystal-grown from a first end toward a second end, and has a step-flow growth region, and a facet. On a cross section passing through a center in a <11-20> direction, an angle θ1 formed by an inside boundary between the facet and the step flow growth region and a crystal growth direction is 56° or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a SiC ingot and a SiC substrate, and a method for evaluating a SiC ingot.

Background Art

[0002] Silicon carbide (SiC) has a breakdown electric field one order of magnitude larger and a bandgap three times larger than that of silicon (Si). In addition, silicon carbide (SiC) has characteristics such as a thermal conductivity about three times higher than that of silicon (Si). Therefore, silicon carbide (SiC) is expected to be applied to power devices, high-frequency devices, high-temperature operation devices, etc. For this reason, in recent years, SiC epitaxial wafers have been increasingly used for semiconductor devices as described above.

[0003] A SiC epitaxial wafer is obtained by laminating a SiC epitaxial layer on the surface of a SiC substrate. The SiC substrate is cut out from a SiC ingot. The SiC ingot is one in which a SiC single crystal has grown on a seed crystal. When a SiC single crystal is grown on a seed crystal, a facet and a step-flow growth region are formed.

[0004] Patent Document 1 describes a method for manufacturing a SiC single crystal. Further, Patent Document 1 describes that when the temperature of the facet region is made lower than that of the non-facet region or the raw material gas concentration of the facet region is made higher than that of the non-facet region from the initial stage to the middle stage of growth, the growth of the facet region and its vicinity is promoted and the area of the facet region becomes smaller.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In recent years, laser processing of SiC ingots has become common. For example, cracks are created in a SiC ingot using a laser, and then SiC substrates are cut out from the ingot. The optimal laser power value when cutting SiC substrates using a laser varies depending on the resistance of the SiC single crystal. If the laser power is too low, sufficient cracks will not be created. Conversely, if the laser power is too high, the SiC single crystal will be damaged.

[0007] The facets of a SiC ingot have lower resistance compared to the step-flow grown regions. Therefore, when cutting a SiC substrate from a SiC ingot, the laser output must be changed at the boundary between the facets and the step-flow grown regions. The more times the laser output is changed during the SiC substrate cutting process, the lower the productivity becomes.

[0008] This invention has been made in view of the above problems, and aims to provide a SiC ingot that is easy to laser process, and a method for manufacturing a SiC substrate using a SiC ingot. [Means for solving the problem]

[0009] The inventors of the present invention focused on the shape of the facets of a SiC ingot and conducted diligent research in order to improve productivity by reducing the number of laser output changes required when cutting a SiC substrate from a SiC ingot by laser processing. As a result, they discovered that it would be effective to use a SiC ingot with facets controlled to a specific shape, and thus conceived the present invention. The present invention provides the following means.

[0010] [1](0001) It consists of a SiC single crystal grown from a first end to a second end, tilted by an offset angle from the plane, and has a step flow growth region and facets, A SiC ingot in which, in a cross-section along the <11-20> direction passing through the center, the angle between the inner boundary between the facet and the step flow growth region and the crystal growth direction is 56° or less.

[0011] [2] The SiC ingot according to [1], wherein the inner boundary extending from the first end toward the second end is inclined at an angle in the [-1-120] direction with respect to the thickness direction toward the second end, which is greater than 0° and less than or equal to 56°.

[0012] [3] A SiC ingot as described in [1] or [2], having a diameter of 149 mm or more. [4] A SiC ingot as described in [1] or [2], having a diameter of 199 mm or more. [5] The SiC ingot according to any one of [1] to [4], wherein the maximum thickness perpendicular to the first end between the first end and the second end is 10 mm or more.

[0013] [6] The SiC ingot according to any one of [1] to [4], wherein the maximum thickness perpendicular to the first end between the first end and the second end is 20 mm or more. [7] A SiC ingot according to any one of [1] to [4], wherein the maximum thickness perpendicular to the first end between the first end and the second end is 30 mm or more. [8] The SiC ingot according to any one of [1] to [4], wherein the maximum thickness perpendicular to the first end between the first end and the second end is 40 mm or more. [9] The SiC ingot according to any one of [1] to [4], wherein the maximum thickness perpendicular to the first end between the first end and the second end is 50 mm or more.

[0014] The process for producing a SiC ingot as described in any of

[10] [1] to [9], The process of processing the SiC ingot into a cylindrical shape, A method for manufacturing a SiC substrate, comprising the step of slicing the SiC ingot that has been processed into a cylindrical shape. A step of preparing a SiC ingot according to any one of

[11] [1] to [9], and a step of slicing the SiC ingot, a method for manufacturing a SiC substrate, comprising.

[0015]

[12] A step of producing a SiC ingot, and a step of processing the SiC ingot into a columnar shape, and a step of slicing the columnar processed SiC ingot to obtain a plurality of evaluation SiC substrates, and a step of measuring the position of the inner boundary between the facet and the step flow growth region in each evaluation SiC substrate, and From the relationship between the position in the cut SiC ingot of each evaluation SiC substrate and the position of the inner boundary of each evaluation SiC substrate, the facet on the cutting plane passing through the center of the SiC ingot and along the <11-20> direction and the step flow growth region calculating a step of calculating an angle formed by the inner boundary and the crystal growth direction, and an evaluation step of evaluating whether the SiC ingot is produced under conditions suitable for producing a SiC ingot sliced by laser processing based on the angle formed by the inner boundary and the crystal growth direction, an evaluation method for a SiC ingot, comprising.

Effect of the Invention

[0016] The SiC ingot of this aspect is composed of a SiC single crystal grown from the first end offset by the offset angle from the (0001) plane toward the second end, and on the cutting plane passing through the center and along the <11-20> direction, the angle formed by the inner boundary between the facet and the step flow growth region and the crystal growth direction is 56° or less. Therefore, the SiC ingot of this aspect can reduce the number of times of changing the laser output when processing into a columnar shape and cutting out a SiC substrate by laser processing, and the SiC substrate can be cut out easily and efficiently.

Brief Description of the Drawings

[0017] [Figure 1]This is a cross-sectional view of the SiC ingot according to this embodiment. [Figure 2] This is a plan view of the SiC ingot according to this embodiment. [Figure 3] This is a cross-sectional view showing an example of a manufacturing apparatus used when manufacturing the SiC ingot according to this embodiment. [Figure 4] This is a cross-sectional view showing another example of a manufacturing apparatus used when manufacturing the SiC ingot according to this embodiment.

Mode for Carrying Out the Invention

[0018] Hereinafter, the manufacturing method of the SiC ingot and the SiC substrate according to this embodiment will be described in detail with reference to the drawings as appropriate. The drawings used in the following description may show the characteristic parts enlarged for the sake of clarity of the characteristics of this embodiment, and the dimensional ratios of each component may be different from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto, and it can be appropriately changed and implemented without changing the gist (technical requirements).

[0019] In this specification, the individual orientation is indicated by [], the collective orientation is indicated by <>, the individual plane is indicated by (), and the collective plane is indicated by {}. Regarding negative indices, in crystallography, "-" (bar) is attached above the number, but in this specification, a negative sign is attached before the number.

[0020] First, the directions are defined. The crystal growth direction of the SiC ingot 10 is defined as the Z direction. The Z direction is the height direction of the substantially cylindrical SiC ingot 10. One direction of the plane orthogonal to the Z direction is defined as the X direction. The X direction is, for example, the <11-20> direction. For example, the +X direction is the [11-20] direction, and the -X direction is the [-1-120] direction. Also, in the plane orthogonal to the Z direction, the direction orthogonal to the X direction is defined as the Y direction. The Y direction is, for example, the <1-100> direction.

[0021] "SiC ingot" Figure 1 is a cross-sectional view of the SiC ingot 10 according to this embodiment. Figure 2 is a plan view of the SiC ingot 10 according to this embodiment shown in Figure 1, viewed from the Z direction. The SiC ingot 10 has a roughly cylindrical shape and is a single crystal of SiC grown from the first end 1 to the second end 2 as shown in Figure 1. The SiC ingot 10 may be a pre-processed cylindrical object or one that has not yet been processed into a cylindrical shape. The second end 2 is the end in the direction of crystal growth. The first end 1 and the second end 2 are connected by a side wall 3. The SiC ingot 10 may expand in diameter from the first end 1 to the second end 2, or it may be a cylindrical object with a constant diameter.

[0022] The first end 1 is a surface inclined by an offset angle from the (0001) plane (Si plane). The second end 2 is a surface inclined by an offset angle from the (000-1) plane (C plane). The second end 2 faces the first end 1. The first end 1 and the second end 2 may have an offset angle of, for example, 0.1° to 8° in the <11-20> direction, and no offset angle in the <1-100> direction. Note that the offset angle of the SiC ingot is not limited to this example.

[0023] The diameter D of the SiC ingot 10 is, for example, 145 mm or more, preferably 149 mm or more, more preferably 150 mm or more, even more preferably 151 mm or more, and may also be 199 mm or more. The diameter D of the SiC ingot 10 is, for example, 305 mm or less. The diameter D of the SiC ingot 10 may be, for example, 230 mm or less, preferably 220 mm or less, more preferably 205 mm or less, and even more preferably 201 mm or less.

[0024] Here, the diameter D of the SiC ingot 10 is the minimum diameter of the SiC ingot 10 and corresponds to the minimum diameter of the SiC substrate obtainable from the SiC ingot 10. As shown in Figure 1, for example, if the SiC ingot 10 has a shape that expands in diameter from the first end 1 to the second end 2, the diameter of the first end 1 corresponds to the diameter D of the SiC ingot 10. For example, if the SiC ingot 10 is cylindrical with a constant diameter, the diameter of any cross-section obtained by cutting the SiC ingot 10 with a plane perpendicular to the Z direction corresponds to the diameter D of the SiC ingot 10. The SiC ingot 10 may be capable of obtaining, for example, a 6-inch substrate or an 8-inch substrate.

[0025] The thickness of the SiC ingot 10 is the maximum thickness perpendicular to the first end 1 between the first end 1 and the second end 2. The thickness of the SiC ingot 10 is, for example, 10 mm or more, preferably 20 mm or more, more preferably 30 mm or more, even more preferably 40 mm or more, even more preferably 50 mm or more, and particularly preferably 60 mm or more. The thickness of the SiC ingot 10 may also be 100 mm or more. A thicker SiC ingot 10 is preferable because it allows for the acquisition of more SiC substrates. The thickness of the SiC ingot 10 is also, for example, 300 mm or less.

[0026] The SiC ingot 10 has facets 4 and step flow growth regions 5. The SiC ingot 10 consists of a SiC seed crystal and a crystal growth portion grown on the SiC seed crystal. The SiC seed crystal used has an offset angle with respect to the {0001} plane. This is because step-flow growth of a SiC single crystal on the SiC seed crystal can suppress the generation of heteromorphic crystals. The offset angle of the SiC seed crystal with respect to the {0001} plane is, for example, 3.5° or more and 4.5° or less, and preferably 4°.

[0027] Even when a SiC single crystal is grown using step flow growth on a SiC seed crystal, during the growth of the SiC single crystal, a portion of the crystal growth plane becomes parallel to the (0001) plane, and a plane parallel to the (0001) plane is exposed on the crystal growth plane. Since the crystal grows perpendicular to the (0001) plane on this plane parallel to the (0001) plane, step flow growth does not occur. Facet 4 of the SiC ingot 10 is a region where the crystal grew perpendicular to the (0001) plane. Facet 4 is a substantially circular region when viewed from the Z direction, as shown in Figure 2. The step flow growth region 5 is a region where a SiC single crystal has been grown using step flow growth on the SiC seed crystal. As shown in Figure 2, the step flow growth region 5 is formed to surround facet 4. The step flow growth region 5 has an offset angle with respect to the {0001} plane. The offset angle of the step flow growth region 5 with respect to the {0001} plane is, for example, 3.5° or more and 4.5° or less, and preferably 4°.

[0028] Facet 4 and step-flow growth region 5 have different colors when viewed from the Z direction (crystal growth direction) of the SiC ingot 10. This is because the crystal growth patterns of facet 4 and step-flow growth region 5 are different. Facet 4 is observed visually as a region with a darker color than step-flow growth region 5. Therefore, the boundary between facet 4 and step-flow growth region 5 can be confirmed visually.

[0029] The boundary between facet 4 and step flow growth region 5 when the SiC ingot 10 is viewed from the Z direction can be determined visually, but it can also be determined using the following procedure. First, an image of the SiC ingot 10 viewed from the Z direction in a plan view is acquired. The image can be acquired using, for example, a scanner. For example, a Canon flatbed scanner can be used. The image may also be acquired using a digital camera.

[0030] Next, the acquired image is converted to the HLS color space, which consists of hue, brightness, and saturation, and the brightness is determined. Then, in the image converted to a brightness distribution, a circle with radius X pixels is drawn with an arbitrary pixel as the center. If there is a pixel within this circle whose brightness difference from the center pixel is Y or greater, the pixel at the center of the circle becomes a facet candidate pixel. If there is no pixel within this circle whose brightness difference from the center pixel is Y or greater, the pixel at the center of the circle becomes a non-facet candidate pixel. Next, the same process is performed on all pixels in the image, and each pixel is classified as either a facet candidate pixel or a non-facet candidate pixel. Then, the boundary between facet candidate pixels and non-facet candidate pixels is detected, and the area inside this boundary can be designated as a facet. Note that among facet candidate pixels, pixels that are isolated from other facet candidate pixels can be determined to be non-facet candidates. The radius X of the circle and the brightness difference Y are set according to the size of the image and the number of pixels. These settings should be set to values ​​that do not significantly deviate from the visual results and the judgment results. For example, if a 640-pixel x 480-pixel image containing a 150mm diameter wafer obtained from a SiC ingot is used, the radius X is 9 pixels and the brightness difference Y is 4W·sr -1 ·m -2 Set it as follows.

[0031] Even in the XZ cross-section of the SiC ingot 10, the boundary between facet 4 and the step-flow growth region 5 can be visually determined. Hereinafter, among the boundaries between facet 4 and the step-flow growth region 5, the boundary located towards the center of the SiC ingot 10 in the XZ cross-section of the SiC ingot 10 will be referred to as the inner boundary 6, and the boundary outside of the inner boundary 6 will be referred to as the outer boundary 7. In the SiC ingot 10 of this embodiment shown in Figure 1, the inner boundary 6 and the outer boundary 7 are straight lines that are inclined in the -X direction with respect to the Z direction (the crystal growth direction indicated by reference numeral 8 in Figure 1).

[0032] As shown in Figure 1, the inner boundary 6 and the outer boundary 7 move towards the center of the SiC ingot 10 (-X direction: [-1-120] direction) as they approach the second end 2 from the first end 1. In other words, as they approach the second end 2 from the first end 1, facet 4 moves further inward into the SiC ingot 10. As a result, the planar coordinates of facet 4 at the first end 1 are different from those of facet 4 at the second end 2.

[0033] In the actual SiC ingot 10, only the planar coordinates of facet 4 at the first end 1 or the second end 2 can be confirmed, and the planar coordinates of facet 4 inside can only be estimated. Facet 4 is a region that incorporates more dopant elements such as nitrogen than the step flow growth region 5, and therefore has lower resistance and lower light transmittance. For this reason, when processing the SiC ingot 10 into a cylindrical shape and then laser processing it, the laser output conditions for facet 4 and the step flow growth region 5 must be different. For example, if facet 4 exists in a location within the SiC ingot 10 where it is estimated from the planar coordinates of facet 4 at the second end 2 that facet 4 should not exist, the laser output may be insufficient during laser processing. In other words, when processing the SiC ingot 10 into a cylindrical shape and then laser processing it, the likelihood of problems occurring increases.

[0034] In contrast, in the SiC ingot 10 of this embodiment, the angle θ1 between the inner boundary 6 between the facet 4 and the step flow growth region 5 and the crystal growth direction 8 in the XZ cross-section (a cross-section passing through the center and along the <11-20> direction) is 56° or less. Therefore, the positional difference between the planar coordinates of the facet 4 at the first end 1 and the planar coordinates of the facet 4 at the second end 2 is sufficiently small. Consequently, the processing stability is high when the SiC ingot 10 is processed into a cylindrical shape and then laser-processed. The angle θ1 between the inner boundary 6 and the crystal growth direction 8 is preferably 50° or less, more preferably 45° or less, more preferably 40° or less, more preferably 35° or less, and even more preferably 30° or less. The smaller the angle θ1 between the inner boundary 6 and the crystal growth direction 8, the better the processing stability when laser-processing a cylindrical SiC ingot, and therefore it is preferable. Furthermore, a SiC ingot 10 in which the angle θ1 between the inner boundary 6 and the crystal growth direction 8 is 10° or more is easily manufactured and therefore preferable.

[0035] The inner boundary 6 extending from the first end 1 to the second end 2 is preferably inclined at an angle greater than 0° and less than or equal to 56° in the [-1-120] direction with respect to the thickness direction from the first end 1 to the second end 2. In other words, it is preferable that the inner boundary 6 is inclined at an angle less than or equal to -X direction with respect to the Z direction (crystal growth direction indicated by reference numeral 8 in Figure 1). This is because, from the planar coordinates of facet 4 at the second end 2, it can be inferred that no facet 4 exists in the region of the SiC ingot 10 inside the planar coordinates of facet 4 at the second end 2. Therefore, the processing stability when processing the SiC ingot 10 into a cylindrical shape and then laser processing it is further enhanced. The angle of inclination of the inner boundary 6 in the [-1-120] direction with respect to the thickness direction from the first end 1 to the second end 2 is preferably 50° or less, more preferably 45° or less, more preferably 40° or less, more preferably 35° or less, and even more preferably 30° or less.

[0036] In this embodiment, the SiC ingot 10 has a constant angle θ1 between the inner boundary 6 and the crystal growth direction 8 (in other words, the inner boundary 6 is a straight line in the XZ cross-section). The angle θ1 between the inner boundary 6 and the crystal growth direction 8 in the SiC ingot 10 may vary depending on the position in the Z direction. In this case, the average value of the angle θ1 between the inner boundary 6 and the crystal growth direction 8 is treated as the angle θ1 between the inner boundary 6 and the crystal growth direction 8. The angle θ1 between the inner boundary 6 and the crystal growth direction 8 is the average value of the angle θ1 between the inner boundary 6 and the crystal growth direction 8 measured at five different positions in the Z direction.

[0037] In the SiC ingot 10 of this embodiment, as shown in Figure 1, it is preferable that the distance between the inner boundary 6 and the outer boundary 7 in the XZ cross-section increases as it approaches the second end 2 from the first end 1. In other words, it is preferable that the area of ​​facet 4 at the second end 2 is larger than the area of ​​facet 4 at the first end 1. This is because it is possible to suppress the generation of heteromorphic crystals and grow SiC single crystals more stably. Furthermore, it is possible to estimate from the planar coordinates of facet 4 at the second end 2 that facet 4 does not exist in a region within the SiC ingot 10 that is larger than the planar coordinates of facet 4 at the second end 2.

[0038] "Method for manufacturing SiC ingots" Next, a method for manufacturing the SiC ingot 10 according to this embodiment will be described with an example. Figure 3 is a cross-sectional view showing an example of a manufacturing apparatus used when manufacturing the SiC ingot 10 according to this embodiment. The manufacturing apparatus for the SiC ingot 10 shown in Figure 3 comprises a crucible 20, an insulating material 30, a liner quartz tube 40, a quartz tube 50, and a reflectance meter 60.

[0039] The crucible 20 is made of, for example, graphite. The crucible 20 has a housing 21 and a lid 22. A gas discharge passage 23 is formed between the housing 21 and the lid 22. The gas discharge passage 23 is provided at least at one location on the outer surface of the crucible 20, and may be provided at multiple locations. The gas discharge passage 23 may be provided in a ring shape around the circumference of the outer surface of the crucible 20 between the housing 21 and the lid 22. The housing 21 is supported and fixed by a support 24. The lid 22 is suspended by a suspension member 25 and can be moved up and down. The distance between the housing 21 and the lid 22 can be changed by moving the suspension member 25 up and down. That is, the width of the gas discharge passage 23 in the Z direction can be freely designed.

[0040] A seed crystal S and SiC raw material M are placed in the film deposition space A within the crucible 20. Gas sublimated from the SiC raw material M recrystallizes on the surface of the seed crystal S, causing a SiC single crystal, which will become the crystal growth portion of the SiC ingot 10, to grow. Residual gas in the film deposition space A is discharged to the outside of the crucible 20 through the gas discharge channel 23.

[0041] The atmospheric pressure in deposition space A during crystal growth should be between 0.3 Torr and 10 Torr. If the pressure in deposition space A is too low, dopant elements such as nitrogen cannot be sufficiently supplied to the crystal, resulting in a high resistivity of the SiC ingot 10. The resistivity of the SiC ingot 10 is a parameter that affects laser processing. Conversely, if the pressure in deposition space A is too high, insufficient sublimation gas will be generated from the SiC raw material M, leading to decreased productivity.

[0042] The bulk density of the graphite constituting the sides of crucible 20 is 1.75 g / cm³. 3 Super 2.00g / cm 3The value should be less than [value missing]. Some of the residual gas in the film deposition space A permeates through the crucible 20 and escapes to the outside. If the bulk density of the graphite constituting the crucible 20 is low, a large amount of residual gas will be discharged from parts other than the gas discharge channel 23. The residual gas discharged from parts other than the gas discharge channel 23 will degrade the insulation material 30. On the other hand, if the bulk density of the graphite constituting the crucible 20 is too high, the thermal conductivity of the graphite will become too high, making it impossible to achieve an appropriate temperature distribution inside the crucible 20.

[0043] The volume G of graphite constituting the crucible 20 shall be between 1.5 and 4.0 times the volume F based on the diameter of the seed crystal S. The volume F corresponds to the dot product of the crucible 20, and when the diameter of the seed crystal S is d, it is π × d 3 It can be calculated by multiplying by 2. If the volume G of graphite constituting the crucible 20 is small, the amount of residual gas permeating the crucible 20 increases, and the insulation material 30 deteriorates. If the volume G of graphite is too large, the thickness of the crucible 20 becomes too thick, making it impossible to achieve an appropriate temperature distribution inside the crucible 20.

[0044] The insulating material 30 is approximately cylindrical and is positioned to surround the crucible 20. The volume of the insulating material 30 is more than 1 times but less than 3 times the volume of the crucible 20. The volume of the insulating material 30 is the volume of the insulating material 30 itself and the volume of the region surrounded by the outer and inner surfaces of the insulating material 30. The volume of the crucible 20 is the internal volume surrounded by the outer surface of the crucible 20. By keeping the volume of the insulating material 30 within the above range, an appropriate temperature distribution can be achieved inside the crucible 20. The temperature distribution inside the crucible 20 affects the formation of facet 4.

[0045] The outer diameter of the insulation material 30 shall be between 1.2 and 1.5 times the outer diameter of the crucible 20. The insulation material 30 located on the side of the crucible 20 is in direct contact with the crucible 20, which generates heat through induction heating, and is therefore prone to deterioration of its insulation performance. By keeping the outer diameter of the insulation material 30 within the above range, deterioration of the insulation material 30 can be prevented while maintaining an appropriate temperature distribution inside the crucible 20.

[0046] The liner quartz tube 40 is positioned around the insulating material 30. At least a portion of the liner quartz tube 40 faces the end of the gas discharge passage 23. Residual gas discharged from the gas discharge passage 23 is blown onto the liner quartz tube 40, adheres to its inner wall, and solidifies. The reflectivity of the liner quartz tube 40 increases due to the adhesion of the solidified residual gas. The liner quartz tube 40 is supported by a support 41. As the support 41 moves up and down, the liner quartz tube 40 also moves up and down. During crystal growth, the liner quartz tube 40 is moved downward at a constant speed.

[0047] The quartz tube 50 surrounds the crucible 20, the insulating material 30, and the liner quartz tube 40. The quartz tube 50 is covered by an upper lid 51 and a lower lid 52. The quartz tube 50 facilitates control of the atmosphere within the film deposition space A.

[0048] The reflectance meter 60 measures the reflectance of the portion of the liner quartz tube 40 that is irradiated with residual gas discharged from the gas discharge channel 23. The reflectance of this portion increases as the amount of gas discharged from the gas discharge channel 23 increases. In the SiC ingot manufacturing apparatus 10 shown in Figure 3, the amount of gas discharged from the gas discharge channel 23 is evaluated by the change in the reflectance of the liner quartz tube 40.

[0049] During crystal growth, the liner quartz tube 40 moves downward at a constant speed due to the support 41. Therefore, the position of the irradiated residual gas in the liner quartz tube 40 is constantly changing. If the amount of gas discharged from the gas discharge passage 23 is constant, the reflectance of the portion of the liner quartz tube 40 whose reflectance is measured by the reflectance meter 60 will be constant.

[0050] In order to manufacture a SiC ingot 10 in which the angle θ1 between the inner boundary 6 between facet 4 and step flow growth region 5 and the crystal growth direction 8 is 56° or less, it is necessary to keep the flow of sublimation gas in the deposition space A approximately constant. When the amount of gas discharged from the gas discharge channel 23 changes, the flow of sublimation gas in the deposition space A changes. In the SiC ingot manufacturing apparatus shown in Figure 3, if the reflectance of the liner quartz tube 40 being measured by the reflectance meter 60 changes during crystal growth, the suspension member 25 can be moved up and down to change the width of the gas discharge passage 23. This makes the amount of gas discharged from the gas discharge passage 23 approximately constant.

[0051] For example, if the reflectance of the liner quartz tube 40 being measured by the reflectance meter 60 decreases during crystal growth, the amount of gas discharged from the gas discharge channel 23 decreases, so the width of the gas discharge channel 23 is widened. For example, if the reflectance of the liner quartz tube 40 being measured by the reflectance meter 60 changes significantly during crystal growth, the amount of gas discharged from the gas discharge channel 23 increases, so the width of the gas discharge channel 23 is narrowed.

[0052] In the manufacturing method of the SiC ingot 10 of this embodiment, as described above, the amount of gas discharged from the gas discharge passage 23 can be controlled by changing the width of the gas discharge passage 23 in the manufacturing apparatus shown in Figure 3. This makes it possible to control the temperature distribution and sublimation gas flow within the film deposition space A, and to manufacture the SiC ingot 10 according to this embodiment in which the angle θ1 between the inner boundary 6 between the facet 4 and the step flow growth region 5 and the crystal growth direction 8 is 56° or less.

[0053] (Other examples) The SiC ingot 10 according to this embodiment may be manufactured using the manufacturing method described below. Figure 4 is a cross-sectional view showing another example of a manufacturing apparatus used when manufacturing the SiC ingot according to this embodiment. The manufacturing apparatus for the SiC ingot 10 shown in Figure 4 comprises a crucible 20, an insulating material 30, a quartz tube 50, a weight measuring instrument 70, and an evaluation substrate 71.

[0054] The SiC ingot manufacturing apparatus shown in Figure 4 is equipped with an evaluation substrate 71 in place of the liner quartz tube 40 in the SiC ingot manufacturing apparatus shown in Figure 3, and a weight measuring instrument 70 in place of the reflectance measuring instrument 60. The configuration of the crucible 20, heat insulating material 30, and quartz tube 50 in the SiC ingot manufacturing apparatus shown in Figure 4 is the same as that of the SiC ingot manufacturing apparatus shown in Figure 3.

[0055] In the SiC ingot manufacturing apparatus shown in Figure 4, residual gas discharged from the gas discharge passage 23 is blown onto the evaluation substrate 71. The residual gas blown onto the evaluation substrate 71 adheres to the surface of the evaluation substrate 71 and solidifies. The weight of the evaluation substrate 71 increases due to the solidified residual gas.

[0056] The weight measuring device 70 measures the weight of the evaluation board 71. If the gas discharge rate from the gas discharge passage 23 is constant, the acceleration of the weight increase of the evaluation board 71 is constant. Conversely, if the gas discharge rate from the gas discharge passage 23 increases, the rate of weight increase of the evaluation board 71 increases. Also, if the gas discharge rate from the gas discharge passage 23 decreases, the rate of weight increase of the evaluation board 71 decreases. In the SiC ingot manufacturing apparatus shown in Figure 4, the amount of gas discharged from the gas discharge passage 23 is evaluated by the change in the weight increase rate of the evaluation substrate 71.

[0057] In the method of manufacturing the SiC ingot 10 using the manufacturing apparatus shown in Figure 4, the amount of gas discharged from the gas discharge passage 23 can be controlled by changing the width of the gas discharge passage 23, similar to the case when using the manufacturing apparatus shown in Figure 3. This allows control of the temperature distribution and sublimation gas flow within the film deposition space A, and enables the production of the SiC ingot 10 according to this embodiment in which the angle θ1 between the inner boundary 6 between the facet 4 and the step flow growth region 5 and the crystal growth direction 8 is 56° or less.

[0058] In the manufacturing method described above, an example of how to evaluate the amount of gas discharged from the gas discharge channel 23 was explained using the change in reflectance of the liner quartz tube 40 or the change in weight of the evaluation substrate 71. However, the physical quantities used to evaluate the amount of gas discharged from the gas discharge channel 23 are not limited to reflectance and weight.

[0059] In the SiC ingot 10 of this embodiment shown in Figure 1, the shape of the facets 4 is controlled such that the positional difference between the planar coordinates of the facets 4 at the first end 1 and the planar coordinates of the facets 4 at the second end 2 is sufficiently small. The SiC ingot 10 of this embodiment can be processed by known methods to produce a SiC ingot that is a cylindrical SiC single crystal.

[0060] In the cylindrical SiC ingot, similar to the SiC ingot 10 of this embodiment, the angle θ1 between the inner boundary 6 between the facet 4 and the step flow growth region 5 and the crystal growth direction 8 in the XZ cross-section (a cross-section passing through the center and along the <11-20> direction) is 56° or less. Therefore, in the SiC ingot 10 of this embodiment, the positional difference between the planar coordinates of the facet 4 at the first end 1 and the planar coordinates of the facet 4 at the second end 2 is sufficiently small, which reduces the number of times the laser output needs to be changed when cutting out the SiC substrate, and allows for easy and efficient cutting of the SiC substrate. The SiC ingot may have an orientation flat or notch for determining the direction of the crystal axis.

[0061] "Method for manufacturing SiC substrates" The method for manufacturing a SiC substrate according to the first embodiment comprises the steps of: producing the SiC ingot 10 of the above embodiment by any of the methods described above; processing the SiC ingot 10 into a cylindrical shape; and slicing the cylindrical SiC ingot. A known method can be used for the process of processing the SiC ingot 10 into a cylindrical shape. Furthermore, for the process of slicing the SiC ingot, for example, a method can be used in which cracks are created in the SiC ingot by laser processing to cut out the SiC substrate.

[0062] In this embodiment, the multiple SiC substrates cut from the SiC ingot all have the same characteristics as the SiC ingot 10 of this embodiment: in the XZ cross-section (a cross-section passing through the center and along the <11-20> direction), the angle θ1 between the inner boundary 6 between the facet 4 and the step flow growth region 5 and the crystal growth direction 8 is 56° or less. Furthermore, if all of the multiple SiC substrates cut from the same SiC ingot have an angle θ1 between the inner boundary 6 and the Z direction (crystal growth direction) of 56° or less, then the SiC ingot before cutting can be said to correspond to the SiC ingot according to this embodiment.

[0063] The method for manufacturing a SiC substrate according to the second embodiment comprises the steps of preparing the SiC ingot 10 according to the above-described embodiment and slicing the SiC ingot 10. The process of preparing the SiC ingot 10 may include obtaining the SiC ingot 10 of the above-described embodiment from another company, and the SiC ingot 10 may be boule as long as it satisfies the requirements of the above-described embodiment. The process of slicing the SiC ingot is the same as in the first embodiment. Alternatively, the SiC ingot 10 may be processed into a cylindrical shape before slicing.

[0064] "Method for evaluating SiC ingots" The evaluation method for the SiC ingot 10 of this embodiment comprises the steps of: manufacturing the SiC ingot 10 of this embodiment as described above; processing the SiC ingot 10 into a cylindrical shape; slicing the cylindrically processed SiC ingot to obtain a plurality of evaluation SiC substrates; measuring the position of the inner boundary 6 between the facet 4 and the step flow growth region 5 on each evaluation SiC substrate; calculating the angle θ1 between the inner boundary 6 between the facet 4 and the step flow growth region 5 and the crystal growth direction 8 on the cross-section along the <11-20> direction passing through the center of the SiC ingot 10, based on the relationship between the position of each evaluation SiC substrate in the cut SiC ingot and the position of the inner boundary 6 of each evaluation SiC substrate; and an evaluation step.

[0065] In the evaluation process, the angle θ1 between the inner boundary 6 and the crystal growth direction 8 of the SiC ingot 10 is used to evaluate whether the SiC ingot 10 was manufactured under conditions suitable for producing SiC ingots that are sliced ​​by laser processing. Specifically, the evaluation step preferably involves evaluating that if the angle θ1 with respect to the crystal growth direction 8 is 56° or less, the SiC ingot 10 was manufactured under conditions suitable for producing a SiC ingot that will be sliced ​​by laser processing, and if the angle θ1 with respect to the crystal growth direction 8 is greater than 56°, the SiC ingot 10 was manufactured under conditions unsuitable for producing a SiC ingot that will be sliced ​​by laser processing.

[0066] Furthermore, in the evaluation method for the SiC ingot 10 of this embodiment, the position of the inner boundary 6 is measured for each of several evaluation SiC substrates that have been prepared in advance, and the angle θ1 between the inner boundary 6 and the crystal growth direction 8 is calculated using the results, thereby evaluating the shape of the facets in other SiC ingots manufactured by the same manufacturing method as the SiC ingot 10. For this reason, the evaluation method for the SiC ingot 10 of this embodiment can be evaluated with high accuracy to determine whether the facets in other SiC ingots have a controlled shape suitable for SiC ingots sliced ​​by laser processing.

[0067] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to any particular embodiment, and various modifications and changes are possible within the scope of the gist of the present invention (technical requirements) as described in the claims. [Examples]

[0068] "Example 1" Using the SiC ingot manufacturing apparatus shown in Figure 3, two SiC ingots with a diameter of 160 mm and a thickness of 32.6 mm were fabricated while controlling the temperature distribution and sublimation gas flow in the deposition space A by adjusting the gas discharge volume from the gas discharge passage 23.

[0069] The SiC ingot of Example 1 was viewed visually from the Z direction (crystal growth direction) in a planar view. As a result, the SiC ingot of Example 1 had a step flow growth region and facets. In addition, one of the two SiC ingots of Example 1 was cut along the <11-20> direction passing through the center, and the inner boundary 6 between facet 4 and the step flow growth region 5 in the XZ cross-section was visually confirmed, and the angle θ1 between the inner boundary 6 and the Z direction (crystal growth direction) was measured. As a result, θ1 was found to be 27°.

[0070] Furthermore, another SiC ingot 10 from Example 1 was processed into a cylindrical shape to create a SiC ingot with a diameter of 150 mm. Cracks were made in the obtained SiC ingot by laser processing, and 75 SiC substrates with a thickness of 0.35 mm were cut out.

[0071] Laser processing was performed with a scan pitch of 200 μm, a laser scan feed rate of 200 mm / sec, one scan cycle, an acceleration / deceleration time of 0.1 seconds, and a line-to-line travel time of 0.1 seconds. The acceleration / deceleration time is the time required to accelerate or decelerate when scanning the laser in the opposite direction after scanning in one direction. The line-to-line travel time refers to the time spent moving in the X direction in a process that repeatedly involves laser scanning in the Y direction and movement in the X direction.

[0072] Using the method described above, the time required to cut 75 SiC substrates from the SiC ingot of Example 1 was 778 minutes. Therefore, the time required to cut one SiC substrate was 10.4 minutes.

[0073] Example 2 Except for adjusting the gas discharge rate from the gas discharge passage 23 to a different value than in Example 1, two SiC ingots were fabricated in the same manner as in Example 1.

[0074] The SiC ingot of Example 2 was viewed visually from the Z direction (crystal growth direction) in a planar view. As a result, the SiC ingot of Example 2 had a step flow growth region and facets. Furthermore, one of the two SiC ingots of Example 2 was cut along the <11-20> direction passing through the center, and the inner boundary 6 between facet 4 and the step flow growth region 5 in the XZ cross-section was visually confirmed, and the angle θ1 between the inner boundary 6 and the Z direction (crystal growth direction) was measured. As a result, θ1 was found to be 45°.

[0075] Furthermore, another SiC ingot, Example 2, was processed into a cylindrical shape in the same manner as the SiC ingot of Example 1 to obtain a SiC ingot with a diameter of 150 mm. Cracks were made in the obtained SiC ingot by laser processing in the same manner as in Example 1, and 75 SiC substrates with a thickness of 0.35 mm were cut out.

[0076] Using the method described above, the time required to cut 75 SiC substrates from the SiC ingot of Example 2 was 833 minutes. Therefore, the time required to cut one SiC substrate was 11.1 minutes.

[0077] "Comparative Example 1" Except for the absence of a gas discharge passage 23, the same crucible used in Example 1 was used, and two SiC ingots with a diameter of 159 mm and a thickness of 28 mm were produced by growing crystals in the sealed crucible.

[0078] The SiC ingot of Comparative Example 1 was viewed visually from the Z direction (crystal growth direction) in a planar view. As a result, the SiC ingot of Comparative Example 1 had a step flow growth region and facets. Furthermore, one of the two SiC ingots of Comparative Example 1 was cut along the <11-20> direction passing through the center, and the inner boundary 6 between facet 4 and the step flow growth region 5 in the XZ cross-section was visually confirmed, and the angle θ1 between the inner boundary 6 and the Z direction (crystal growth direction) was measured. As a result, θ1 was found to be 62°.

[0079] Furthermore, another SiC ingot, Comparative Example 1, was processed into a cylindrical shape in the same manner as SiC ingot 10 in Example 1 to obtain a SiC ingot with a diameter of 150 mm. Cracks were made in the obtained SiC ingot by laser processing in the same manner as in Example 1, and 64 SiC substrates with a thickness of 0.35 mm were cut out.

[0080] Using the method described above, the time required to cut 64 SiC substrates from the SiC ingot of Comparative Example 1 was 761 minutes. Therefore, the time required to cut one SiC substrate was 11.9 minutes.

[0081] The SiC ingots of Examples 1 and 2 required less time to cut out a single SiC substrate than the SiC ingot of Comparative Example 1. This is because, compared to the SiC ingot of Comparative Example 1, the number of laser power changes required when cutting out the SiC substrate from the SiC ingot of Examples 1 and 2 was less.

[0082] Examples 1 and 2 and Comparative Example 1 show the results for SiC ingots with a processed diameter of 150 mm. SiC ingots with a processed diameter of 200 mm were also prepared and evaluated in the same way. Similar evaluation results were confirmed for the SiC ingots with a processed diameter of 200 mm as for the SiC ingots with a processed diameter of 150 mm. In other words, in the SiC ingots manufactured under the conditions of this embodiment, the angle θ1 between the inner boundary 6 and the Z direction (crystal growth direction) in the XZ cross-section was 56° or less. In the SiC ingots manufactured under conditions that did not satisfy this embodiment, the angle θ1 was greater than 56°. Furthermore, compared to the SiC ingots manufactured under conditions that did not satisfy this embodiment, the time required to cut out one SiC substrate was shorter for the SiC ingots manufactured under the conditions of this embodiment. [Explanation of Symbols]

[0083] 1 1st end 2 2nd end 3 side wall 3 4 Facets 5-Step Flow Growth Area 10 SiC ingots 20 Crucible 21 Storage Unit 22 Lid 23 Gas discharge channel 24 Support 25 Suspension member 30 Insulation 40 Liner Quartz Tubes 41 Support 50 quartz tube 51 Top lid 52 Lower lid 60 Reflectance meter 70 Weight measuring device 71 Evaluation board

Claims

1. (0001) It consists of a SiC single crystal grown from a first end to a second end, inclined by an offset angle from the plane, and has a step flow growth region and facets. A SiC ingot in which, in a cross-section along the <11-20> direction passing through the center, the angle between the inner boundary between the facet and the step flow growth region and the crystal growth direction is 56° or less.

2. The SiC ingot according to claim 1, wherein the inner boundary extending from the first end toward the second end has an angle of inclination in the [-1-120] direction with respect to the thickness direction toward the second end that is greater than 0° and less than or equal to 56°.

3. The SiC ingot according to claim 1, wherein the diameter is 149 mm or more.

4. The SiC ingot according to claim 1, wherein the diameter is 199 mm or more.

5. The SiC ingot according to claim 1, wherein the maximum thickness perpendicular to the first end between the first end and the second end is 10 mm or more.

6. The SiC ingot according to claim 1, wherein the maximum thickness perpendicular to the first end between the first end and the second end is 20 mm or more.

7. The SiC ingot according to claim 1, wherein the maximum thickness perpendicular to the first end between the first end and the second end is 30 mm or more.

8. The SiC ingot according to claim 1, wherein the maximum thickness perpendicular to the first end between the first end and the second end is 40 mm or more.

9. The SiC ingot according to claim 1, wherein the maximum thickness perpendicular to the first end between the first end and the second end is 50 mm or more.

10. The SiC ingot according to claim 1, wherein the inner boundary approaches the center as it moves from the first end towards the second end.

11. The SiC ingot according to claim 1, wherein the angle between the inner boundary and the crystal growth direction varies depending on the position in the crystal growth direction.

12. A step of producing a SiC ingot according to any one of claims 1 to 11, The process of processing the SiC ingot into a cylindrical shape, A method for manufacturing a SiC substrate, comprising the step of slicing the SiC ingot that has been processed into a cylindrical shape.

13. The method for manufacturing a SiC substrate according to claim 12, wherein the step of slicing the SiC ingot is performed by laser processing.

14. A step of preparing a SiC ingot according to any one of claims 1 to 11, A method for manufacturing a SiC substrate, comprising the step of slicing the SiC ingot.

15. The method for manufacturing a SiC substrate according to claim 14, wherein the step of slicing the SiC ingot is performed by laser processing.

16. The process of manufacturing SiC ingots, The process of processing the SiC ingot into a cylindrical shape, A process of slicing the cylindrical SiC ingot to obtain multiple evaluation SiC substrates, A process of measuring the position of the inner boundary between the facet and the step flow growth region in each evaluation SiC substrate, A step of calculating the angle between the inner boundary between the facet and the step flow growth region and the crystal growth direction, based on the relationship between the position of each evaluation SiC substrate cut out in the SiC ingot and the position of the inner boundary of each evaluation SiC substrate, and the position of the inner boundary of the facet and the step flow growth region in the cut surface passing through the center of the SiC ingot along the <11-20> direction, A method for evaluating a SiC ingot, comprising an evaluation step of evaluating whether the SiC ingot was manufactured under conditions suitable for producing a SiC ingot that is sliced ​​by laser processing, based on the angle between the inner boundary and the crystal growth direction.

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